An arrangement for direct current with contacts for a bottom electrode in the vicinity of the ladle bottom is known from German Unexamined Application for Patent OS 31 07 454. The object of this invention is to eliminate the space problem in ladles and ladle furnaces. It does not concern itself with solving the problem of the feeding of energy to the bottom electrodes.
A terminal for detachably connecting electric-current and coolant transfer is known from German Unexamined Application for Patent OS 35 35 690. The connection can be a screw, wedge or clamp connection. When changing the contact electrode, the contact points on the terminal are detached by the operating personnel in order to separate the electric cable and the coolant conduits from the contact electrode. The attaching or detaching of the contact electrode is thus subject to the disadvantage that the operating personnel must work under difficult ergonomic conditions.
One of the objects of the present invention is to create a maintenance-free and easily interchangeable apparatus which renders it possible to connect the counterelectrode automatically and reliably to the power line leading to the energy source.
To achieve this object there is provided an apparatus for the thermal treatment of a metallic melt comprising a metallurgical vessel for receiving the melt, the vessel having an outer jacket; means for electrically heating the melt comprising at least one electrode positioned above the melt and at least one counterelectrode in contact with the melt; first means on the outer jacket and connected to the counterelectrode for transferring electrical energy to the counterelectrode, the transfer means comprising a first contact plane; second means for transferring electrical energy to the first transfer means, the second transfer means comprising a second contact plane; and means operatively connected to the second transfer means for mechanically positioning the contact plane of said second transfer means in electrical energy conducting relation with the contact plane of the first transfer means. Preferably, the means for electrically heating the melt comprises a D.C. arc heating device.
In accordance with the invention, and upon depositing the metallurgical vessels such as ladles or distributors at the respective processing station, the electric contact with the bottom electrode is produced without any activity on the part of the operating personnel.
The contact planes or surfaces which are connected to the source of energy are provided at the processing stations such as, for example, at the vacuum unit, at a rotary tower or on the premises of the foundry which can be reached by a plant vehicle. These contact surfaces or planes can be brought, with respect to their vertical and horizontal arrangement at the processing station, in contact with respective surfaces of current feed elements for the bottom electrode attached to the vessel. A dimension which must be taken into consideration in this connection the feet or the support elements of the vessel such as, for instance, suspension loops or carrying claws as well as the distance from a vessel wall.
The contact surfaces are preferably arranged in the vicinity of the bottom of the metallurgical vessel. A particularly suitable location for the transfer elements is the outer jacket of the metallurgical vessel since matching support elements can be provided at the various processing stations, such as the rotary tower or the vacuum unit, and the mounting thereof can be assured more easily there.
The respective contact surfaces have a size which assures dependable transmission of energy. Several contacts can also be attached on the circumference of the vessels.
Graphite is provided as contact material, it being mechanically wear-resistant as well as resistant to pressure and temperature and it has the capacity to transmit electrical energy with low losses. The contact elements are made readily exchangeable for easy maintenance.
Possible accumulation of dirt is counteracted by specially designing the contact surface as described herein. Accordingly, the support surface of at least one of the elements for the transmission of energy is preferably divided into individual segments. A maximal snug-fit effect can be achieved for the outer contact surfaces by developing the surface segments from individual graphite bodies which can compensate for small changes of movement thereof in the direction of the contact pressure.
In another advantageous development of the invention the counterelement is developed as a pocket which is filled with graphite powder. In this way a close contact between the contacting surfaces is achieved.
In order to assure dependable contact of the total contact areas in rough operation the invention provides for a substantially vertical or horizontal compensation. For this purpose the structural parts which are in contact with the source of energy are mounted on springs or else are moveable along their longitudinal axis and in contact with a pressure accumulator. This measure assures constant pressure of the contacts against each other which can furthermore be regulated if necessary. In addition, the contact surfaces are tiltable with respect to the vertical or horizontal plane.